The present invention is generally related to a tilt-trim subsystem assembly for marine propulsion devices, and, more particularly, to a tilt-trim subsystem assembly for a stern drive propulsion system.
In marine propulsion devices, it is common to have hydraulic cylinder/piston assemblies located externally of the boat for effecting pivotal movement of the propulsion unit relative to its a mounting bracket. For example, in marine propulsion devices of the aid stern drive or inboard/outboard type, it is common to have hydraulic cylinder/piston assemblies connected between the gimbal ring and the propulsion unit for effecting tilting movement of the propulsion unit relative to the gimbal ring. In other types of marine propulsion devices, such as outboard motors, it is known to have hydraulic cylinder/piston assemblies connected between the mounting bracket and the propulsion unit for effecting steering and/or tilting movement of the propulsion unit relative to the mounting bracket.
In many of these marine propulsion devices having hydraulic assemblies located externally of the boat, means are provided for supplying hydraulic fluid to the hydraulic assemblies from a source of fluid inside the boat. The source of fluid may be connected to an hydraulic circuit also inside the boat that pressurizes and distributes the hydraulic fluid through a manifold interconnecting respective hydraulic lines to the respective hydraulic cylinder assemblies outside the boat. The hydraulic circuit may typically include a pressure pump, and an electric motor coupled to drive the pump. This configuration generally presents several issues. One issue is whether to run the hydraulic lines over the transom or through the transom and, if through the transom, how to seal the opening through which the hydraulic lines pass. Another issue is how to protect the portions of the hydraulic lines extending externally of the transom. For example, the hydraulic lines may be exposed to a relatively harsh external environment, e.g., ocean water, sun rays, and other factors that may promote galvanic corrosion, or other deterioration to the line material. Any deterioration of the lines may be further aggravated due to the bending that the lines may be subject to as the propulsion unit is tilted upwardly and downwardly. This may lead to leaks and a relatively short hydraulic line life. Further, such tilt/drive subsystems may take valuable room in the interior of the boat and require additional holding fixtures and additional labor to install on the boat floor or transom. U.S. Pat. No. 5,032,094 appears to describe a tilt-trim subsystem that uses an intricate external assembly including separate tilt and trim cylinders to provide tilt and trim to an outboard propulsion unit and that may somewhat alleviate some of the above-discussed issues that may develop in outboard units, unfortunately such subsystem does not overcome any of such issues as may be encountered in boats using a stern drive propulsion system since the configuration described in the foregoing patent is strictly limited to outboard designs. Thus, it is desirable to provide a tilt-trim subsystem assembly that, with a lesser number of components, and consequently even more inexpensively and reliably than known assemblies, allows for providing tilt and trim to a stern drive propulsion system that is not subject to the foregoing problems and that can be easily installed either as a replacement kit or as part of an original installation. The increased reliability of the tilt-trim subsystem of the present invention and its ease of service are likely to result in enhanced durability at a lower cost to pleasure boat users and others.